67 research outputs found
Grey-box models for flood forecasting and control
No full textHochwasservorhersage und -management sind wesentliche Bestandteile der Hydrologie und finden große Beachtung bei der Vermeidung von Überschwemmungen und Dürren, die Leben oder materielle Verluste kosten können. Auf Grund dieser Aspekte ergibt sich eine Notwendigkeit der entwickelten Techniken, um Wasserressourcen erfolgreich zu steuern. Aktuelle Entwicklungen
auf dem Gebiet der Kontrolle konzentrierten sich auf die Entwicklung von Vorhersagesystemen, die rechnerisch einfache Modelle fordern, um diese in ein Optimierungssystem zu implementieren. Daten-gestützte Modelle sind bekannt für geringe rechnerische Anforderungen. Auf Grund von Einschränkungen, wie begrenzte Extrapolationsfähigkeiten und mangelnden physikalischen Übersetzungen, entsteht die Motivation zur Entwicklung von Grey-Box-Modellen. Diese verbinden physikalisches Wissen mit einer datengesteuerten Komponente, um den Bereich der Gültigkeit des Modells, sowie das physikalische Verständnis der einzelnen Komponenten des Modells zu erhöhen. In der vorliegenden Arbeit wurden zwei wichtige Grey-Box-Modelle für eine hydrologische und eine hydraulische Abflussberechnung entwickelt. Das hydrologische Grey-Box-Modell besteht aus der Kontinuitätsgleichung der Masse
und einem künstlichen neuralen Netz als Ersatz der Impulsgleichung, welches den Abfluss als Funktion in Abhängigkeit von der Speicherung und des Zuflusses wiedergibt. Das hydraulische Grey-Box-Modell berücksichtigt ebenfalls die Kontinuitätsgleichung, aber der Impuls wird durch eine Funktion ersetzt, welche den Wasserstand flussaufwärts und flussabwärts berechnet und es erlaubt, Rückstaueffekte abzubilden. Das hydrologische Modell wurde in einem
numerischen und einem realen Fall (São Francisco Fluss - Brasilien) getestet. Das hydraulische Modell wurde ebenfalls in einer numerischen und einem realen Fall (Main - Deutschland) getestet. Für beide Fälle wurden zwei Steuerungstechniken implementiert: die Proportional-Integral Control (PI) und die Model Predictive Control (MPC). Für die Betrachtung des Mains wurde ein Hochwasservorsorge-Ereignis mit der Vorhersehbarkeit der MPC-Steuerung getestet. Ergebnisse zeigen, dass die entwickelten Techniken ähnliche Leistung wie die hochdetaillierten Modelle aufweisen, und die Validierung in den Kontrollprüfungen zeigt, dass diese Modelle in Echtzeit-Steuerungen vielversprechend in der Umsetzung sind.Flow forecasting and management are essential fields of study in hydrology to mitigate floods and droughts that can cause life or material losses. These undesired aspects arise the necessity of developing techniques to successfully control water resources. Recent developments in the control community have focused on the development of predictive control techniques, which demand
computationally inexpensive models to be employed in optimization schemes. Data-driven models are well-known for low computational demand. However, their limitations, such as limited extrapolation capabilities and lack of physical meaning, arises the motivation for the development of grey-box models, which couples physically-based knowledge with a data-driven component, so as to increase the range of validity of the model, as well as to allow the physical understanding of each component of the model.
In the present work we develop two types of grey-box models for flow routing, one hydrological and the other hydraulic. The hydrological grey-box model is composed by the mass continuity equation for mass balance and the replacement of the momentum equation by an Artificial Neural Network which reproduces the discharge as a function of the storage and inflow. The hydraulic grey-box model implements also the mass-continuity component, but the momentum equation is replaced by a function which accounts for the water level
upstream and downstream, enabling the reproduction of backwater effects. The hydrological model is tested in an academic and a real-world case (São Francisco River, Brazil). The hydraulic model is tested also in an academic and a real-world case (Main river, Germany). For both cases, we also implemented two control techniques: Proportional-Integral Control (PI) and Model Predictive Control (MPC). In the Main river case we tested a flood prevention event
using the predictability of MPC control. Results shows that the developed techniques have similar accuracy with highly-detailed models, and the validation in the control tests shows that these models are promising as regards implementing in real-time control systems
Efficiency of Exciton and Charge Carrier Photogeneration in a Semiconducting Polymer
No full textEuan Hendry, Juleon M. Schins, L. P. Candeias, L. D. A. Siebbeles, and Mischa Bonn, Physical Review Letters, Vol. 92, article 196601 (2004). "Copyright © 2004 by the American Physical Society."We determine the efficiencies for the formation of excitons and charge carriers following ultrafast photoexcitation of a semiconducting polymer (MEH-PPV). The simultaneous, quantitative determination of exciton and charge photoyields is achieved through subpicosecond studies of both the real and the imaginary components of the complex conductivity over a wide frequency range. Predominantly excitons, with near-unity quantum efficiency, are generated on excitation, while only a very small fraction (<10-2) of free charges are initially excited, consistent with rapid (∼100 fs) hot exciton dissociation. These initial charges are very short lived, decaying on subpicosecond time scales
Ultrafast charge generation in a semiconducting polymer studied with THz emission spectroscopy
No full textEuan Hendry, Mattijs Koeberg, Juleon M. Schins, L. D. A. Siebbeles, and Mischa Bonn, Physical Review B, Vol. 70, article 033202 (2004). "Copyright © 2004 by the American Physical Society."We study the ultrafast charge generation in a semiconducting polymer (MEH-PPV) by measuring the radiated THz field after photoexciting the biased polymer with a femtosecond visible pulse. The subpicosecond temporal characteristics of the emitted wave reflects the ultrafast photoconductivity dynamics and sets an upper limit for charge generation of 200 fs following photoexcitation, and reveals the dispersive nature of charge transport in MEH-PPV. A comparison of the fields radiated from MEH-PPV and the well-characterized model semiconductor system (GaAs) allows for an accurate estimate of the quantum efficiency for charge generation in the polymer, found to be less than 1% . Both observations are consistent with ultrafast charge generation in semiconducting polymers through hot exciton dissociation
Project website www.blue-action.eu (D8.3)
No full textAbout this document
Deliverable: D8.3
Work package in charge: WP8 Communication, Dissemination, Engagement and Exploitation
Actual delivery date for this deliverable: Project-month 2
Dissemination level: The general public (PU)
Lead author(s)
Danish Meteorological Institute: Chiara Bearzotti
Other contributing author(s)
SAMS: Euan Paterson
Summary
The website www.blue-action.eu has been set up in December 2016 for ensuring that we “promote the action and its results, by providing targeted information to multiple audiences (including the media and the public) in a strategic and effective manner” (Art. 38.1 of the Grant Agreement).
The website has been set up by the Project Office at DMI, with tools made available by MPI-M. During the lifetime of the project, the website will be populated with additional sections related to the presentation of the project tools and results.We support the Blue Growth!
Visit us on: www.blue-action.eu
Follow us on Twitter: @BG10Blueactio
Interchain effects in the ultrafast photophysics of a semiconducting polymer: THz time-domain spectroscopy of thin films and isolated chains in solution
No full textEuan Hendry, Mattijs Koeberg, Juleon M. Schins, H. K. Nienhuys, V. Sundström, L. D. A. Siebbeles, and Mischa Bonn, Physical Review B, Vol. 71, article 125201 (2005). Copyright © 2005 by the American Physical Society.We compare the generation and decay dynamics of charges and excitons in a model polymer semiconductor (MEH-PPV) in solution and drop-cast thin films, by recording the sub-ps transient complex conductivity using THz time-domain spectroscopy. The results show that the quantum efficiency of charge generation is two orders of magnitude smaller in solution (~10–5) than in the solid film (~10–3). The proximity of neighboring chains in the films apparently facilitates (hot) exciton dissociation, presumably by allowing the electron and hole to separate on different polymer strands. For both samples, photoexcitation leads to the predominant formation of bound charge pairs (excitons) that can be detected through their polarizability. Surprisingly, the polarizability per absorbed photon is a factor of 3 larger in solution than in the film, suggesting that interchain interactions in the film do not result in a substantial delocalization of the exciton wave function
Systematic review and narrative synthesis of the experiences of individuals with chronic pain participating in digital pain management interventions.
No full textBACKGROUND: The use of digital pain management interventions has grown since the Covid 19 pandemic. The aim of this study was to systematically review and synthesise evidence from qualitative studies regarding the experiences of individuals with chronic pain participating in digital pain management interventions in primary care and community settings. METHODS: Fourteen databases were searched, as well as citation tracking and hand-searching reference lists of included articles. The latest search was completed by 07/07/2023. Qualitative studies of patient and carer perspectives of digital pain management interventions for adults aged 18 and over with non-malignant chronic pain were included. All studies were appraised for quality using the Critical Appraisal Skills Programme Qualitative Checklist. A narrative synthesis approach was used to synthesise the findings. Normalisation Process Theory was used to understand how individuals with chronic pain make sense of digital pain management interventions and incorporate knowledge, skills and strategies learnt into their day-to-day lives. RESULTS: Eleven studies, encompassing both digital applications for use on smartphones/ mobile devices and user-directed online modular programmes, were included in the synthesis. Three main themes and related subthemes were identified from the included studies: 1) Making sense of the digital intervention (Subthemes: Tailoring to user's needs; Human contact and support; Accessibility of the digital intervention; Personal and environmental factors affecting engagement with digital interventions); 2) Initiating and Maintaining Behaviour Change (Subthemes: Planning activity; Being active); and 3) Personal Growth (Subthemes: Gaining understanding and skills; Gaining and acting on feedback; Negotiating a new relationship with pain). CONCLUSION: Recommendations. The key recommendations from our findings are that digital pain management interventions should provide: Specific and tailored information for individual participants.Focus on changing attitudes and behaviours and reframing perceptions of pain.Structured goal setting with prompts to review goals.Potential healthcare professional support alongside the digital intervention.Limitations of the review. To reduce bias, it would have been preferable for more than one author to independently fully analyse each paper and to identify themes and sub-themes. Instead, the identified themes and sub-themes were discussed with two other authors in the team (ES, LW) to reach a consensus view on final themes and sub-themes. One author (JS) received a Research Internship and Research Initiation Award funded by NIHR Applied Research Collaboration (ARC) Wessex (https://www.arc-wx.nihr.ac.uk/) and NHS England (https://www.england.nhs.uk/). The protocol for this review was registered with the National Institute of Health Research (NIHR) PROSPERO international database for registering systematic reviews (PROSPERO Registration Number CRD42021257768)
Euan Uglow: The Complete Paintings
No full text244pp
This book is a catalogue raisonne in which the author (Lampert) has inspected some 400 works over a six year period, beginning with interviews with the artist in the last four months of his life. Lampert has also written the principle essay (a second one is by the art historian Richard Kendall) reassessing his contribution to British painting in the late 20th century
Simultaneous ultrafast probing of intramolecular vibrations and photoinduced charge carriers in rubrene using broadband time-domain THz spectroscopy
No full textMattijs Koeberg, Euan Hendry, Juleon M. Schins, Hendrik A. van Laarhoven, Cees F. J. Flipse, Klaus Reimann, Michael Woerner, Thomas Elsaesser, and Mischa Bonn, Physical Review B, Vol. 75, article 195216 (2007). "Copyright © 2007 by the American Physical Society."We determine the ultrafast frequency- and time-resolved complex dielectric responses of photoexcited, single-crystal rubrene in the frequency range of 10–30 THz (330–1000 cm−1) using ultrafast broadband THz spectroscopy. In this frequency range, we observe the response of both photogenerated mobile charges and intramolecular vibrational modes simultaneously, both of which vary with time after excitation. The data in conjunction with a theoretical model indicate a dynamic blueshift of the 15.5 THz phonon
- …
